Study On Value Determination System For Determing The Reference Level Of Each Progeny In The ²²²Rn/²²⁰Rn Chamber

For accurate evaluation of ²²²Rn/²²⁰Rn daughter dose levels in the environment,standard reference level setting methods are required to calibrate or scale the measuring instrument.The currently in the established reference level setting method at home and abroad cannot directly measure the count information of all progeny in the ²²²Rn/²²⁰Rn chamber,which will cause a certain error.Predecessor based on the?-?spectroscopy method established based on the decay characteristics of²²²Rn/²²⁰Rn progeny,can directly obtain the count information of each progeny,which correspondingly reducing the error transmitted along the decay chain,improving the measurement of ²²²Rn/²²⁰Rn progeny precision.Based on this method,we have studied value determination system for determining the reference level of each progeny in the²²²Rn/²²⁰Rn chamber.Firstly,a value determination system is constructed based on the measurement principle and measurement requirements of the?-?energy spectrum method.Then we optimized the sampling device to obtain two parallel samples at a time.In order to improve the experimental efficiency,the measurement program was further optimized,and the key parameters in the experimental equipments were studied and measured.The work of this paper lays a fundation for the standardization resesrch of the value determination method in the future.After the improvement of the sampling device,parallel samples can be obtained,which can effictively shorten the sampling time and reduce the influence of continuous sampling on the fluctuation of daughters'concentration.Then we used MATLAB to simulate the variation of ²²²Rn/²²⁰Rn daughters'measurement error with sampling time and measurement time,and re-determined the measurement program.After the improvement,in the pure ²²²Rn,pure ²²⁰Rn,²²²Rn/²²⁰Rn mixed environment,the total measurement time is shortened from 121min,246min,317min to 70min,110min,95min.The maximum different between the error of the improved measurement program and the error of the original measurement program is less than 0.02.When researching the key parameters of the experimental device,in the process of?detection efficiency calibration of the ²²²Rn/²²⁰Rn daughter body,we revised the probe size through MCNP,and supplemented the detection efficience of RaC on the HPGe?detector on the basis of modified size.After analysis,it is considered that RaC is more suitable for alpha energy spectrum measurement.Finally,the total uncertainty of the experimental devices is given.When the ²²²Rn/²²⁰Rn daughter concentration is high,the error caused by the statistical fluctuation of the daughter count can be ignored.At this time,the total uncertainty of the value determination system is 6.93%.After experimental verification,the ²²²Rn/²²⁰Rn daughter reference level setting method based on?-?spectrum can be used as a new reference level setting method,which is expected to improve the level of environmental dose monitoring in the future.